Where a heat exchanger system so reduces the temperature of combustion gases as to condense much of the water vapor therein, problems arise how to dispose of the condensate. As to that part of the condensate which forms within a tubed heat exchanger, the condensate may partially clog the tubes unless suction is applied. Such suction is therefore applied to a manifold at the outlet side of the heat exchanger. This gives rise to the problem how to drain condensate from the negative pressure in the manifold to the atmosphere.
Such a suction blower, as shown in my U.S. Pat. No. 4,478,206 dated Oct. 23, 1984, also supplies positive pressure in the flue stack to partly remedy the lack of natural draft of the cool flue gases. As the cool flue gases rise slowly, further condensation occurs in the flue. This presents the problem how to provide drainage of condensate from the flue stack without loss of such positive pressure.
In U.S. Pat. No. 4,194,488, dated Mar. 25, 1980, condensate formed in a tubed heat exchanger and condensate formed in a flue stack are shown to be separately drained by simple drain outlets, not protected by any traps. The communication of atmospheric pressures through such drains would seemingly impair the positive or negative pressures necessary for optimum operation of the system. It is not known whether other patents or publications deal with this problem.